Author Topic: don't use a microcontroller  (Read 4528 times)

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Offline cooldogTopic starter

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don't use a microcontroller
« on: November 09, 2007, 06:57:31 PM »
i want to try and make a robot but i don't want to program a microcontroller
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Offline Steve Joblin

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Re: don't use a microcontroller
« Reply #1 on: November 09, 2007, 07:08:29 PM »
then you want a BEAM robot... Solarbotics sells some nice kits.

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Re: don't use a microcontroller
« Reply #2 on: November 09, 2007, 07:38:31 PM »

Offline cooldogTopic starter

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Re: don't use a microcontroller
« Reply #3 on: November 10, 2007, 02:33:03 PM »
if i don't use a microcontroller to my robot and just stick photocells is between the power and the motors will it work?
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Offline HDL_CinC_Dragon

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Re: don't use a microcontroller
« Reply #4 on: November 10, 2007, 04:12:36 PM »
well technically... yeah... it will go faster in the light and slower in the dark in that case
Photocells have a higher resistance in the dark thus when it is dark, less voltage will be getting to the motors.
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Offline cooldogTopic starter

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resistors
« Reply #5 on: November 10, 2007, 08:24:33 PM »
i am dirrectly puting a photocell in betwwen the power source (12v) without a microcontroller. do i need resistor if so what one.

also i want to take my 12v power and turn it down to 9v because the motors are only rated for 9.6 what resistor or other device do i need
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Offline Steve Joblin

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Re: resistors
« Reply #6 on: November 10, 2007, 08:38:49 PM »
A photocell is also called a "photoresistor" or a "light dependent resistor"... that is to say, it is a resistor (just one where the resistance varies depending on how much light (or how little light) is shining on it.  To this end, you do not need a resistor, as the unit itself is a resistor.

If you wish to reduce the voltage, I would use PWM.  Using a resistor is not an efficient way as you are just burning away power as heat.

Offline cooldogTopic starter

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Re: resistors
« Reply #7 on: November 10, 2007, 08:40:29 PM »
what r PWM's
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Offline airman00

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Re: resistors
« Reply #8 on: November 10, 2007, 08:55:21 PM »
pulse width modulation

basically switches on and off quickly to make speed control or dimming

http://www.bluemelon.org/index.php/Products/BlueSense_Open_Collector_Outputs/PWM_explanation

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Offline cooldogTopic starter

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Re: don't use a microcontroller
« Reply #9 on: November 11, 2007, 06:38:21 AM »
i tryed this and the robot won't go anywhere any ideas
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Offline Admin

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Re: don't use a microcontroller
« Reply #10 on: November 11, 2007, 07:00:57 AM »
Well you actually need an amplifier and transisters n stuff . . .

Try this:
http://www.robotroom.com/Sandwich.html

Offline cooldogTopic starter

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Re: don't use a microcontroller
« Reply #11 on: November 11, 2007, 07:07:05 AM »
what do i need to get from the site ( E.G. printed circut board )
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Re: don't use a microcontroller
« Reply #12 on: November 11, 2007, 07:16:55 AM »
Its instructions on how to make a line follower robot without a microcontroller. It will explain it all.

Offline Rebelgium

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Re: don't use a microcontroller
« Reply #13 on: November 11, 2007, 10:16:59 AM »
You can't just place some photoresistors between the source and the motors, the photoresistors will burn because the motors draw to much current.
And possibly the resistance of the photR's is way to high (very likely 1-10K) and the motors will not get enough voltage to turn. This last is probably what happened with you.

I can see you're not an expert in electronics ;) , no big deal, so I recommend you buy a kit ( The suggested Boebot is a great way to start!)
Or make the robot you got the link to at robotroom.
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Offline Robotboy86

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Re: don't use a microcontroller
« Reply #14 on: November 12, 2007, 09:43:21 AM »
This kinda peaked my intrest :)

Wouldn't the best way to do this(without a mcu) be something like this:

DC -> H-bridge -> Motor
Small DC -> Photoresistor 1 -> T1,T4 -> Motor spins!
Small DC -> Photoresistor 2 -> T2,T3 -> Motor spins!

H-bridge is designed like so:

transistor 1, top right corner of h-bridge, 2 is top left, 3 is bottom right, 4 is bottom left.  Of course the photo resistors would always be giving SOME power to the h-bridge.. as it will never completly resist the charge.  This would cause the robot to kind of swirve around in uneven light, and in even light drive a semi-straight line.  It would also have the effect of making it turn into shade.. 

The transistors would always be suppying SOME power beacuse they do not act as on/off switches in varying voltage enviroments such as this.. if it were setup to be only .5v or 8.5v(or something like that) then it would work..

but chances are it would see things like 1v-12v in varying levels.

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Re: don't use a microcontroller
« Reply #15 on: November 12, 2007, 11:11:40 AM »
hmmmm you don't want a resistor in series with a motor.

instead, you want the photoresistor output value (probably amplified with an op-amp) to control the gate of your transistor. the transistor then controls the motor.

Offline cooldogTopic starter

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Re: don't use a microcontroller
« Reply #16 on: November 12, 2007, 12:23:21 PM »
where can i get a op-amp

where to get a transistor



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Re: don't use a microcontroller
« Reply #17 on: November 12, 2007, 01:23:51 PM »
Always check the parts list for robot parts:
http://www.societyofrobots.com/robot_parts_list.shtml

Electronics can be found at:
digikey.com
mouser.com

Offline cooldogTopic starter

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Re: don't use a microcontroller
« Reply #18 on: November 12, 2007, 01:30:48 PM »
what r the product  # because there are so many or can you be more pesific
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Re: don't use a microcontroller
« Reply #19 on: November 12, 2007, 01:41:12 PM »
Product number for what?

You need a schematic before you can decide on part #'s :P

That sandwich robot tutorial lists parts . . . In the end, we can't make your robot. You will have to figure this out . . . look at the parts online and see if they fit with what you want it to do.

After you make your schematic and select parts, feel free to post it and we will error check it for you.

Offline Rebelgium

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Re: don't use a microcontroller
« Reply #20 on: November 12, 2007, 05:33:34 PM »
Quote
This kinda peaked my intrest Smiley

Wouldn't the best way to do this(without a mcu) be something like this:

DC -> H-bridge -> Motor
Small DC -> Photoresistor 1 -> T1,T4 -> Motor spins!
Small DC -> Photoresistor 2 -> T2,T3 -> Motor spins!

H-bridge is designed like so:

transistor 1, top right corner of h-bridge, 2 is top left, 3 is bottom right, 4 is bottom left.  Of course the photo resistors would always be giving SOME power to the h-bridge.. as it will never completly resist the charge.  This would cause the robot to kind of swirve around in uneven light, and in even light drive a semi-straight line.  It would also have the effect of making it turn into shade..

The transistors would always be suppying SOME power beacuse they do not act as on/off switches in varying voltage enviroments such as this.. if it were setup to be only .5v or 8.5v(or something like that) then it would work..

but chances are it would see things like 1v-12v in varying levels.
That's not right,
An H-bridge is built with FET's or MOSFET's , one of the properties of these is that they are 100% on of 100% off. not something in between, if you would use them in between (eg 50%) the dissipated pwer in the FETs will be waaaay to much causing the FET's to burn... Or as Admin would say, "bad stuff will happen"  ;)

Quote
You need a schematic before you can decide on part #'s Tongue

That sandwich robot tutorial lists parts . . . In the end, we can't make your robot. You will have to figure this out . . . look at the parts online and see if they fit with what you want it to do.

After you make your schematic and select parts, feel free to post it and we will error check it for you.
Exactly what I was going to say, we can't make it for you, you need to put some effort in it...

My advice is,
- use a microcontroller, it may seem scary at first, but it's much easier in the end... the only robots you can make without a muC is a photovore, and if you decide to make a photovore then:
- search a schematic for the robot you wish to build , It's much easier to copy that persons robot then to reinvent the wheel... I might be wrong, but I suspect you're just not ready for building your own invented robot. :) Find the schematic on this site, or on one of the links on this site, or google.
- When you have the schematic , order/purchase all components, build it, and test it!
« Last Edit: November 13, 2007, 01:05:28 PM by Rebelgium »
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Offline cooldogTopic starter

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Re: don't use a microcontroller
« Reply #21 on: November 12, 2007, 06:01:44 PM »
thanks i am going to use a microcontroller after all

just a question, the stampy robot could i take the circutboard and microcontroller with scaning sharp IR upgrade form the $50 robot and put it in the stampy robot chasi to work the same
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Re: don't use a microcontroller
« Reply #22 on: November 12, 2007, 07:40:08 PM »
cooldog, yes, you can modify the chassis as you like. For your first robot just copy someone else's design, and then get creative for your second robot.

As Rebelgium was saying, if you are making a high power circuit such as a motor controller, make sure you check datasheets of the components you use for power ratings. If your 6V circuit has 10 amps going through it (6V*10A = 60 W), but your mosfet (or whatever) is rated for 30 W, bad stuff will happen :P

Offline cooldogTopic starter

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Re: don't use a microcontroller
« Reply #23 on: November 12, 2007, 07:50:27 PM »
okay but will then stampy robot work the same as in your video because i see you use a different circut board
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Re: don't use a microcontroller
« Reply #24 on: November 12, 2007, 08:00:20 PM »
Im betting you haven't seen this yet
http://www.societyofrobots.com/robot_50_robot_sharpIR.shtml

Its how to add the stampy algorithm to your $50 robot.

Offline cooldogTopic starter

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Re: don't use a microcontroller
« Reply #25 on: November 12, 2007, 08:29:11 PM »
yes i have
i was just checking if they were the same
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